Electric furnace.



No. 837,277. PATENTED DEC. 4, 1906. K. BIRKELAND 8: S. EYDE.

ELECTRIC FURNACE. APPLICATION IIL'BD NOV. 10. 1904.

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N0- 83'7,277. PATENTED DEC. 4, 1906. K. BIRKELAND & S. EYDB.

ELECTRIC FURNACE.

APPLICATION FILED NOV.10. 1904.

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mlrzessea. 194 kw UNITED STATES PATENT OFFICE.

KRISTIAN BIRKELAND AND EYDE, or OHRISTIANIA, NORWAY.

ELECTRIC FURNACE.

Specification of Letters Patent.

Patented Dec. 4, 1906.

Application filed November 10, 1904. Serial No. 232.232.

To all whom it may concern:

Be it known that we, KRISTI'AN'BIRKE- LAND and SAMUEL EYDE, subjects ofthe King of Sweden and Norway, residing at Christiania, Norway, haveinvented certain new and useful Improvements in Electric Furnaces; andwe do hereby declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it appertains to make and use the same, reference being hadto the accompanying drawings, and to letters of reference markedthereon, which form a part of this specification.

This invention relates to electrical furnaces used in the chemicalindustry to create chemical reactions under the influence of theelectrical arcs.

The invention relates more especially to the class of electricalfurnaces described in United States Letters Patent No. 775,123, datedNovember 15, 1904, in which an arc is made use of which is dispersed bymeans of a ma netic field.

he object of the present invention is to improve this class of furnaces,so that they may advantageously be run with alternating currents, eitherfor the electrodes or for the field-magnet windings, or in both.

It is also an object of this invention to provide means whereby it ismade possible to increase the ratio between the furnace tension and thetension of the electric machinery, or, more correctly, to increase theratio between the kilowatts and the kilovoltamperes.

In the drawings, Figure 1 is a diagram showing .the form of a currentcurve in a Birkeland furnace fed with alternating current. Fig; 2 showsan arrangement of the electrodes, and Fig. 3 a detail of a modified formof the electrode-points, the electrode being hollow. Fig. 4 illustratesanother form of electrode arrangement. Fig. 5 shows the generalarrangement of the furnace.

Referring more particularly to Fig. 5, a 11 indicate the electrodes e,the furnace, through the walls of which the electrodes project into thereaction-chamber. f is an electromagnet disposed so as to create a fieldin the chamber around the electrodes. In this instance the electrodesare for the matter of convenience shown disposed axially in relation tothe magnetic field. They may be so dis osed,

althou h it'is' generally foundprefera 'le to' have t em disposed atright angles to the lines of force. The electrode b is shown rotatablymounted and may be provided with a small motor 9, which keeps it inrotation, as will be hereinafter explained more fully.

In the following it is supposed that the generator h for eliveringcurrent to the electrodesis an alternating-current enerator.

In the furnace workin with alternating current the current curve asabout the form indicated in the dia ram, Fig. 1.

If it is attempte to increase the tension for the purpose of obtainingan increase of energy as well as arcs with increased surface by increasithe relative distance between the electrodes,t care will soonbeextinguished i. e., a certain intensity of current and of magnetic filedcorresponds to a certain maximum distance between the electrodes. It isderived from observations that the extinction will always take placewhen the current is about zero. to avoid extinction at this point, itmight be possible to increase the tension materially without having tofear an extinction of the arc. This result may be obtained by runningthe furnace with a resistance in the are,

which alternates in synchronism with thecurrent hase and in such waythat the resistance as its minimum when the current value is passingzero, or the variations in the resistance may be of so much greaterfreuency than the frequency of the current t at an extinction ispractically excluded.

We may obtain the aim of the invention in several ways and we shall hereexplain three different ways, one of which may be termed mechanical, onea magnetical, and one an electrical method. We may, for instance, obtainsuch a result by varying the relative distance between the points of theelectrodes in synchronism with the current phases so as to obtain theshortest distance at the zero-points of the current curve and longerones at the intermediate parts of the curve. Hereby is obtained anincreased average tension and an increased factor of energy, or, inother words, the ratio between the kilowatts and the kilovoltamperes isincreased.

If therefore it was possible corresponding number of'poles.

, call an As it would not be suitable to have the electrodes moving toand from each other n their axial direction, in carrying out this methodwe prefer usin electrodes or roups of electrodes rotating a )out anaxis, w ereby the necessary synchronism may be obtained by aid of asynchronous motor rotating the said electrodes or groups of electrodes.

When using electrodes of the form illustrated in Fig. 2, the electrode ais or may be stationary, while the electrode bis rotatable about itslongitudinal axis, the minimum distance between the electrode pointsbeing only a fraction of their maximum distance, and we may easilyrovide for any desired degree of variation this distance simply byaltering the form of the points of the electrodes.

It is advantageous to provide one or both electrodes with a plurality ofpoints and to have the rotating electrode actuated by a synchronousmotor (not shown) having a Such an arrangement is especially suitablewhen tubular electrodes, as illustrated in Fig. 3, are used.

It is sometimes advantageous to make use of these tubular electrodes forthe purpose of leading the gases or part of them into the furnacethrough the interior of the electrodes, whereby the latter are cooled. YWe may also provide for an arrangement where both electrodes arestationary, but

where there is placed a conductive pointed body d or arc-formerbetween'the said points, I

as illustrated in Fi 4, the said conductive body being rotate orotherwise moved in synchronism with the current phases. The body isshown to have four points, but it may have any other form and any numberof points.

The herein-described devices may also be used for furnaces running withdirect current both on the electrodes and on the magnets.

In the foregoing it has been supposed that the magnetic field has aconstant intensity. It is, however, possible to carry out this inventionwith a pulsating or variable magnetic field, such pulsation having anefi'ect on the factor of energy substantially equivalent with thevariation of the distance between the electrode.

The furnace may be worked with stationary electrodes and alternatingcurrents both in the electrodes and in the field-magnet, obtainingthereby substantially the same result as with moving electrodes.

We may, as hereinbefore mentioned, obtain the result aimed at by way ofwhat we electrical method. This may be done by-connecting the electrodeswith an auxiliary circuit 7c, supplied from a source Z throughcondensers m n, producing a spark discharge of high frequency with hightens1on and low current strengthfor instance, a Tesla current. Suchdischarges may be sald to act as a bridge for the arc of the Workmgcurrent.

Having thus described our invention, what we claim as new therein, anddesire to secure by Letters Patent, is

1. In an electric furnace, the combination of means for creating a manetic field, electrodes placed within said eld, a source of alternatingelectric current capable of forming dispersed arcs between saidelectrodes, and means to vary the resistance of the current in passingbetween the electrodes in synchronism with the phases of the workingcurrent. I

2. In an electric furnace, the combination of means for creating amagnetic field, elec-' trodes placed within said field, a source ofalternating electric current capable of form ing dispersed arcs betweensaid electrodes, and means to vary the distance between the electrodesin synchronism with the phases of the working current.

3. In an electric furnace, the combination of means for creating avariable ma netic field, electrodes placed within the said eld, a sourceof alternating electric current capable of forming dispersed arcsbetween said electrodes, and means to vary the distance between theelectrodes in synchronism with the phases of the field current.

4. In an electric furnace, an electrode formed of a tubular piece ofelectrically-conducting material and having its ends serrated to formone or more points.

5. In an electric furnace, the combination with means for creating avariable magnetic field, a stationary and a movable electrode placedWithin the field, a source of alternating current capable of formingdispersed arcs between said electrodes and means to vary the distancebetween the electrodes in synchronism with the phases of the workingcurrent, substantially as described.

6. In an electric furnace, the combination with means for creating avariable magnetic field, hollow electrodes having eccentric arcformingpoints within the field, a source of alternating current capable offorming dispersed arcs between said electrodes and means to vary thedistance between the arcforming oints of the electrodes in synchronismwit the phases of the working current, substantially as described.

7. In an electric furnace, the combination with means for creating avariable magnetic field, a fixed electrode whose arc-forming end. is outof alinement with the axis of the electrode, a second rotatableelectrode in alinement therewith and whose arc-forming end is also outof alinement with the axis thereof, a

source of alternating current capable of formas our invention we havesigned our names in mg dispersed arcs between said electrodes presenceof two subscnbm witnesses.

and means to rotate the second electrode to KRISTIAN 'IRKELAND. vary thedistance between the ends of the SAMUEL EYDE.

5 electrodes in synchronism with the working Witnesses:

current, substantially as described. MICHAEL ALGER,

In testimony that we claim the foregoing HENRY BoRDEwIcH.

